Pathways of chemical recovery in acidified,metal-contaminated lakes near Sudbury,Ontario, Canada

This paper describes the recovery pathways of two lakes situated near the Coniston nickel-copper smelter. These lakes were exposed to very intense airborne pollution, including SO₂, H₂SO₄, Ni and Cu, during the 60 year operation of the smelter. After the closure of the Coniston smelter in 1972 and the subsequent improvement in air quality, the water quality in both lakes began to improve. Despite their proximity and exposure to similar inputs, the lakes differed both in the rate and magnitude of recovery. This study demonstrates the capacity of lakes to recover from chemical stresses over a very short period. Changes in Cu and Ni concentration could be predicted, while changes in pH, measured as H⁺, could not. The reasons for this discrepancy as well as the processes and lake parameters that control chemical recovery are discussed.     

Biological recovery of two previously acidified,metal-contaminated lakes near Sudbury Ontario,Canada

Studies are reported on two small lakes at Sudbury, Ontario located close to a nickel-copper smelter which closed in 1972. At that stage, Baby Lake had a pH of 4.0–4.2 while the adjacent Alice Lake had a pH 5.9–6.3. Both lakes were almost entirely devoid of algae and had neither Zooplankton nor fish. Soon after the closure of the smelter, with its large airborne volume of sulphur dioxide and of copper and nickel containing particulates, the chemistry of the lakes began to change. By 1985, Baby Lake had changed from pH 4.0 to 6.8 and is now at pH 7.2. The pH of Alice Lake increased from a low of 5.9 in the early 1970s to 6.9–7.4 in the mid 1980s and is now at 7.3. Copper and nickel concentrations also decreased in both lakes during this period. The first biota found in the lakes in the post-smelter stage in the early 1980s were benthic red chironomids, planktonic rotifers, and a limited number of phytoplankton species, of which Rhizosolenia was the most common. By the 1990s, 13 phytoplankton species were present in each lake, with a substantial Zooplankton fauna (14 species) of rotifers, copepods, and cladocerans. There are now numerous insect larvae in the sediment and some small fish in both lakes. The biological recovery, which followed substantial reductions in acidity and in soluble nickel and copper concentrations in the waters, is a slower process than chemical recovery and is initially characterized by the dominance of a few species.     

Evaluating macroinvertebrate responses to recovery from acidification in small lakes in Ontario,Canada

The biomonitoring program of Environment Canada examines food chains in small Ontario lakes to interpret ecological responses of waterfowl and their foods to changing acid deposition. Macroinvertebrates and fish were sampled in three acid-sensitive regions: Muskoka (1991; N=20), Algoma (1992; N=20), and Sudbury (1994; N=22). Small lakes (<11 ha;=" important=" breeding=" habitat=" for=" waterfowl)=" were=" chosen=" to=" cover=" the=" range=" of=" ph=" in=" each=" region,=" and=" include=" those=" with=" and=" without=" fish.=" in=" all=" regions,=" macroinvertebrate=" taxonomic=" richness=" (particularly=" nekton=" and=" benthos)=" was=" greater=" in=" fishless=" lakes=" compared=" to=" lakes=" with=" fish.=" among=" fishless=" lakes,=" taxonomic=" richness=" (especially=" benthos)=" was=" positively=" correlated=" with=" ph,=" although=" regional=" differences=" were=" evident.=" previous=" studies=" near=" sudbury=" have=" shown=" that=" several=" benthic=" groups=" have=" distribution=" and=" abundance=" patterns=" with=" respect=" to=" ph=" (trichoptera,=" ephemeroptera,=" hirudinea,=" amphipoda,=" and=" gastropoda).=" those=" patterns=" continue=" near=" sudbury,=" and=" were=" also=" strongly=" apparent=" in=" algoma.=" in=" all=" regions,=" the=" number=" of=" acid-sensitive=" taxa=" per=" lake=" is=" related=" to=" ph,=" and=" should=" increase=" as=" lakes=" recover=" from=" acidification.=" however,=" predicting=" macroinvertebrate=" responses=" to=" recovery=" must=" consider=" concurrent=" effects=" of=" fish,=" as=" they=" are=" a=" dominant=" factor=" structuring=" these=">     

A Scandinavian model used to predict the reacidification of limed lakes in Nova Scotia and Ontario,Canada

A Scandinavian reacidification model was used to predict the reacidification of three limed lakes in the Sudbury area, Ontario, and Sandy Lake in Nova Scotia. A prediction was made also for the future reacidification of Bowland Lake, 70 km north of Sudbury, limed in 1983. The reacidification of a neutralized lake is dependent on the continuing dilution of the dissolved calcium carbonate, and for a limited period of time, the dissolution of calcite from the bottom. The test of the model on the Canadian laked shows that the model may be a useful tool for lake liming design and planning.     

Lead biogeochemistry in the littoral zones of south-central Ontario lakes,Canada, after the elimination of gasoline lead additives

Stable Pb isotope ratios were used to trace thesources and pathways of Pb between the atmosphere,surficial sediment fractions, the white water-lilyNymphaea odorata, and waters collected at 26littoral sites in 23 Ontario lakes in summer 1993,three years after alkyl Pb additives were finallyeliminated from Canadian gasoline. Based onsimilarities of isotopic composition, the exchange ofPb between lakewater and sediment 'carbonate', andsubsequently between 'carbonate', 'oxide' and othersediment fractions, was the most likely water-sedimentpathway of Pb movement. pH controlled Pb fractionationwithin surficial sediments, with the 'organic' poolcomprising 80–97% of total Pb in most acidic lakesand 15–60% in alkaline lakes. About 28% of the Pb inN. odorata shoots was accumulated directly fromwater, whereas there was no evidence of root uptake ofPb from sediments. The Pb in plant tissues wasisotopically homogeneous and dissimilar to thevariable composition exhibited in ambient waters andsediments. Plant Pb isotopes strongly resembled thehistorical Canadian atmospheric (alkyl Pb) signature.A possible explanation is that, like essential tracemetals, historically-accumulated Pb was highlyconserved during the annual growth cycle of thislong-lived, clonal macrophyte, being storedover-winter in underground rhizomes and recycled intospring growth. Given the low rate of 'new' Pb uptake,historical alkyl Pb may continue to dominate planttissues for some time, even though it was notdetectable in littoral waters and sediments.     

Outcomes of longterm deciduous forest restoration in southwestern Ontario, Canada

At present, forest cover in southwestern Ontario, Canada, remains at less than 5% due to intensive agricultural and urban land use. Although much of the extant forest is increasingly protected by legislation, remnants continue to be degraded by the spread of non-native plant species, overgrazing, and recreational use. Some parks in the region have adopted management programs aimed at mitigating this degradation. Over the last 35 years, cottages and roads at Point Pelée National Park have been removed and sites either passively restored (i.e. road or cottage eliminated and vegetation allowed to regenerate) or actively restored (i.e. road or cottage eliminated, exotic vegetation removed, and native species planted). In 1994 and 1995, we assessed the effectiveness of restoration by comparing the understorey plant communities in 28 restored sites with those in less disturbed reference sites. There was a significant increase (P<0.0001) in the similarity of understorey plant communities between restored and reference sites as time-since-restoration increased. Soil moisture, canopy cover, distance to continuous forest, and site-shape all significantly affected plant species composition. Former road sites recovered significantly (P<0.05) more rapidly than former cottage sites, and the former lawns of passively restored cottage sites were the slowest to recover. Five years following active restoration, non-native ruderal species continued to dominate restored sites. The observed recovery of understorey plant communities in restored sites is attributed to their proximity to natural vegetation, and its function as a seed source. In some sites, recovery is substantial and, assuming present trajectories of change are maintained, we predict that recovery could occur in many mesic sites within the next 20 years. Restoration activity facilitates forest recovery and would appear to have a valuable function in mitigating ongoing conflicts between conservation and human use in this region.     

Evaluation of elemental depletion weathering rate estimation methods on acid-sensitive soils of north-eastern Alberta, Canada

Immobile element-based weathering estimation methods assume that Zr (or Ti) is an immobile element, and that weathering rates of other elements can be estimated according to the enrichment of Zr in weathered horizons relative to an unweathered parent material. This approach was used to estimate base cation weathering rates for 33 soil profiles on acid-sensitive terrain in north-eastern Alberta. Zirconium generally showed enrichment within the rooting zone, but the deepest (subsoil) samples were not always associated with the lowest Zr concentrations. Weathering rates estimated with the Zr depletion and Pedological Mass Balance (PMB) methods were generally low (ranges: 0-51 and 0-58 mmol_c m^− 2 yr^− 1, respectively); however, low base cation oxide concentrations and heterogeneity within soil profiles complicated weathering rate calculations and net base cation gains were calculated for several (six) sites. Evaluation of the Zr depletion and PMB weathering estimates against those calculated with the process-oriented PROFILE model at a subset (n = 9) of the sites indicated the estimates were poorly related, with PROFILE rates typically being higher. The effects-based emissions management strategy for acid precursors in this region requires spatial coverage of soil properties (including weathering rates) across a large area, but the apparent limitations associated with the immobile element based methods in this region: identifying representative parent soils and deriving weathering rate estimates comparable to more robust methods are arguments against their candidacy for future use.     

Hypolimnetic Alkalinity Generation in Two Dilute, Oligotrophic Lakes in Ontario, Canada

It has been observed that the alkalinity concentrations in the hypolimnia of many thermally stratified lakes increase over the duration of the summer. We have quantified the processes, both redox and exchange, that contributed to the alkalinity increases measured in two lakes that are situated on the Precambrian Shield of Ontario, Canada by measuring hypolimnetic mass balances for all substances involved in alkalinity-generating or -consuming reactions. These include nitrate, ammonium base cations, iron, manganese, sulphate, organic anions, as well as alkalinity itself. In one lake, iron reduction was the dominant source of alkalinity; since this process is probably reversed at fall overturn when hypolimnetic waters mix with oxygenated surface waters, the alkalinity generated by this mechanism is likely temporary in nature. In the second lake, iron reduction and sulphate reduction were both important the latter should provide more permanent alkalinity.     

Social Media for Enhancing Stakeholders' Innovation Networks in Ontario,Canada

ABSTRACT

This case study assessed local food stakeholders' use of Facebook and Twitter to support interaction and build their networks of innovation in Ontario. Data were collected using Netlytic ? an online data mining tool from the social media platforms ? and key informant interviews. Findings revealed that stakeholders could be more innovative in their use of social media, but they would be unlikely to do so, without tapping into beneficial interactions of weak ties, as well as fostering strong ties. They also need to utilize the high brokerage role of key facilitating organizations and develop a social media strategy by integrating both ‘online’ and ‘offline’ interactions.     

Frost heaving of soils at two locations in Southern Ontario,Canada

Frost-heave measurements conducted over two winters in frost-susceptible soil at two adjacent Canadian locations, one near Guelph, and the other near Elora, Ontario, are examined in the light of supporting environmental data. The trend in the penetrating frost line, and the total depths achieved in each season at the Guelph site were similar, but surface displacement during 1976–1977 was less than half that recorded in 1975–1976. This disparity is attributed to seasonal variations in the proximity of the water table with respect to the soil freezing level. When the former is deep, closed-system conditions prevail, and frost heave is severely curtailed. The importance of access to water is also demonstrated at the Elora site where frost heaving was sustained by a water table close to the surface despite the presence of a snow cover.     

Heavy metals in fish from a series of metal-contaminated lakes near Sudbury,Ontario

Elevated levels of Ni, Cu, and Zn are present in surficial sediments of lakes in the Sudbury region of northeastern Ontario. Metal concentrations in sediments were highest in lakes closest to local smelters, and decreased rapidly with distance: equations are presented describing these relationships. Several fish species were collected from a series of these metal-contaminated lakes, and analyzed for metal content of muscle, liver, and kidney tissues. Muscle tissue was a poor indicator of increased metal availability. Liver tissue was a good indicator for Cu, while kidney tissue was best for Ni. Zinc levels in tissues varried little among either fish species or lakes. The presence of elevated levels of Cu in liver, and elevated levels of Ni in liver and kidney tissues of fish from certain lakes supported the hypothesis that some fish populations were being stressed by metal additions to local aquatic habitats. Although the degree of lake contamination (as indicated by Cu concentrations in sediments) was one factor influencing Cu availability, water quality parameters such as alkalinity and DOC also appeared to be very important.     

Sulphate in Sudbury, Ontario, Canada, Lakes: Recent Trends and Status

Sulphur emissions from the Sudbury, Ontario, metal smelting industry have affected thousands of lakes in Ontario, Canada. Reductions in these emissions during the 1970's resulted in reduced lakewater SO₄ concentrations and other water quality changes in the 1970's and 1980's. Further declines in lakewater SO₄ concentrations have accompanied additional recent S emission reductions achieved by 1994. Recent (1997) SO₄ concentrations are still related to distance from the Sudbury smelters. A strong inverse relationship with distance is evident to about 45 km, and is most pronounced in lakes within about 20 km. In lakes beyond 45 km, dissolved organic carbon (DOC), which was correlated with hydrological response time and total phosphorus concentrations, was the best correlate with recent SO₄ concentrations, indicating that some slowly-flushing, oligotrophic lakes still exhibit a "Sudbury" effect. Most lakes beyond 45 km, however, showed SO₄ declines and recent SO₄ concentrations comparable to lakes around Dorset, ～200 km from Sudbury, suggesting that these lakes are now most affected by the long-range atmospheric transport of S.     

Crustacean plankton in northeastern Ontario lakes subjected to acidic deposition

During the summer of 1981, crustacean plankton was sampled in 249 northeastern Ontario lakes, including a large proportion of acidic lakes. Species cluster analysis showed that a major species group containing B. longirostris, D. minutus, H. gibberum, and M. edax was common to most lakes. Two species subgroups most associated with more productive waters (D. retrocurva, D. oregonensis, T. p. mexicanus, and Diaphanosoma sp.) and less productive waters (D. longiremis, C. scutifer, D. g. mendotae, C. b. thomasi, E. longispina, and E. lacustris) in the study area were identified. Acidic lakes were characterized by reduced numbers of species related to declines in the importance of cyclopoids, Daphnidae, L. kindtii and E. lacustris and high relative abundance of D. minutus. Stepwise multiple linear regression of physico-chemical lake characteristics against percent composition of individual species failed to explain much of the variation in species proportions. However, variables related to lake thermal structure were most frequently the primary correlates with species proportions in near-neutral lakes while in acidic lakes the best statistical predictors of species percent composition were most often variables directly related to lake acidity.     

Impacts of environmental change on sustainable food production in Southwest Ontario,Canada

A sustainable food production system may be defined as an agri-food sector which over the long term can simultaneously maintain environmental quality, produce a sufficient food supply and provide adequate rewards to primary producers. This paper investigates the implications of two forms of environmental change for sustainable food production in Southwest Ontario, a major agricultural region in Canada. A modified version of the Universal Soil Loss Equation was employed to estimate long-term erosion, whereas an altered climate was derived from a general circulation model. Crop productivity models were used to estimate the impacts of modified environmental conditions on yields. Mathematical programming models were used to estimate economic viability and food production capacity given these changed conditions. Soil erosion combined with a climatic warming induced by a doubling of atmospheric concentrations of CO₂ or its equivalent would contribute to severe declines in resource quality, and result in declines of 18 per cent to 35 per cent in average yields for major grains and oilseeds. On lands with a relatively high natural risk to erosion, the yield-reducing impacts of erosion and a climatic warming would reduce profits from cash grain farming by 26 per cent, and increase concern about the economic viability of these enterprises. Environmental change would reduce the region's food production potential to 86 per cent of current production levels, and possibly endanger the security of its food supplies. These findings suggest the need to explore strategies which would either prevent future environmental change or mitigate its adverse impacts.     

Modelling tillage erosion in the topographically complex landscapes of southwestern Ontario, Canada

A tillage erosion model was developed for southwestern Ontario based on the relationship between tillage translocation and slope gradient and slope curvature. Two studies of tillage translocation and tillage erosion were used to calibrate this model, one a comparison of upslope and downslope tillage translocation on shoulder slopes, the other an examination of tillage translocation throughout topographically complex landscapes. Two field sites were used for validation of the model. For both sites, past tillage practices were known and past soil erosion was determined using ¹³⁷Cs as an indicator of soil redistribution. The model accurately predicted the pattern of soil redistribution that had occurred within the two field sites. Severe soil loss was observed and predicted on convex landscape positions and soil accumulation was observed and predicted on concave landscape positions. The model accounted for almost all of the soil lost from the convex upper slope positions where tillage erosion was expected to be the dominant erosion process. There was considerable soil loss and accumulation elsewhere in the landscapes which could not be accounted for by the model and was presumed to be primarily the result of water erosion. It was concluded that tillage erosion must be incorporated into soil erosion modelling for the purposes of soil conservation.     

Preliminary biochemical observations of fishes inhabiting an acidified lake in Ontario,Canada

Blood serum and other tissues of white suckers (Catostomus commersoni) and other species of fish have been examined in a preliminary effort to understand losses of fish from acid lakes. Maturing females of highly acid George Lake failed to show the normal degree of increase in serum Ca over males captured in the same location. Elevated serum Ca was always observed in females, relative to males, from non-acid locations when maturation stages were similar. A number of body tissues were examined to determine whether the distributions of Ca or other elements were altered and the only striking change evident in fish from George Lake was their high Mn content. Bone in particular was examined for N, Na, Mg, P, K, and Ca and no evidence of demineralization was found. Other tests such as hemoglobin indicated that an anticipated adaptive response to asphyxia was absent. Our results indicate that potential mechanisms of fish losses such as asphyxia and starvation are unlikely to have been significant, however, they do not firmly establish any alternate mechanism. As a working hypothesis we suggest that Ca dynamics may limit ovarian development and that absorption of this metal at exchange surfaces may be impaired.     

Adoption of soil conservation practices: An empirical analysis in Ontario,Canada

Soil degradation threatens environmental quality and sustainable food production. As a result of efforts to promote soil conservation, farmers in Canada are thought to be reasonably aware of both the importance of conservation and the existence of remedial and preventive practices. Despite this, the adoption of conservation practices has been less than overwhelming. Forces other than awareness and positive attitude seem to be constraining many land managers from employing available conservation methods. This paper presents the findings from an empirical investigation of the use of soil conservation practices and barriers to their adoption in the southwestern region of Ontario, Canada. The analysis is set in the context of literature on technology adoption. A scheme for measuring farm-level conservation effort is developed, and barriers to adoption are derived from an analysis of a range of independent physical, personal, and economic factors, and from the obstacles or constraints identified by producers themselves. Key barriers relate to economic pressures, the complexity and compatibility of practices, and perceptions regarding the actual need for practices. The findings have relevance for the design of public policies and programs, notably the importance of supplying information on farm-level implications of conservation methods and the need for a stable economic environment for agriculture to allow longer-term planning.     

Short range variability of soil chemistry in three acid soils in Ontario,Canada

Abstract

The objective of this study was to assess the efficacy of soil sampling and analysis methodologies used in Canada's Acid Rain National Early Warning System (ARNEWS). During July and August of 1992, twenty‐five soil pits were sampled and analyzed for available phosphorus (P); exchangeable potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), aluminum (Al), sodium (Na), sulfate‐sulfur (SO4‐S), boron (B), and molybdenum (Mo); total nitrogen (N), P, K, Ca, Mg, Fe, Cu, Mn, Zn, Al, Na, sulfur (S), B, nickel (Ni), lead (Pb), and organic matter (O.M.); pH; and cation exchange capacity (C.E.C.) at three ARNEWS sites across Ontario. The soils were: i) a till‐derived Ferro‐Humic Podzol (Humic Haplorthod), ii) a Humo‐Ferric Podzol (Haplorthod) developed in coarse glaciofluvial sand, and iii) a Dystric Brunisol (Dystrochrept). The three sites were similar in chemical composition except for available P, exchangeable Ca, Mn, total Mn, O.M., and pH. Sample numbers calculated to achieve ±10% error with 95% confidence were much higher in mineral horizons than in forest‐floor horizons. Organic macro‐elements and pH were found to be the least variable parameters while micro‐elements were significantly more variable. Analyses are categorized into groups requiring similar numbers of samples. Other studies have found comparable levels of variability and their results are compared to coefficients of variation generated by the Ontario results. Variability within a pit was also observed and found to be less than that found across each 20‐ x 20‐m site but still very significant. Overall, the variability results from other studies appear to be applicable to Ontario acid soils for common analyses. Investigations observing micro‐elements, or which require high levels of accuracy, should incorporate pilot studies to ascertain the degree of variability for their location.     

Recent Temporal Patterns in the Chemistry of Small,Acid-sensitive Lakes in Central Ontario,Canada

We monitored the chemistry of 603 small water bodies in three acid-sensitive regions of central Ontario, Canada (Algoma n=235, Muskoka n=216, Sudbury n=152) between 1988^-1996 to determine whether they have responded to recent SO2 emission reductions, and whether any chemical changes were related to lake characteristics. During the study, 27-56% of lakes declined in SO₄ ^2- concentrations, 41-57% declined in base cation concentrations, but only 26-28% increased in pH or ANC (acidity status). Increases in pH were greatest in lakes with low ANC, but had weak relationships to lake color or volume. No consistent trends were observed for DOC, NO₃ ^- or TP concentrations. Clearly, the long-term biological recovery of these sensitive aquatic ecosystems will depend on interactions among several environmental stressors, including acidification.